Establish and maintain an animal-virus disease model, which closely mimics a disease state in man, for the rapid evaluation of antivirals as directed by the Project Officer. The antivirals should be evaluated for prophylaxis, therapy and toxicity. During the interlude between evaluation of antivirals, the investigator will do further studies with the animal models to refine them and develop baseline data for more effective antiviral evaluation. The role of interferon and interferon inducers should be evaluated and used as the background for comparison of new antivirals. The administration of the challenge virus should be such that the animal is not overwhelmed. The challenge should be as close to normal infection as possible. Hopefully this will result in disease in perhaps 80% of the animals. The parameters listed below should be considered in the evaluation of the antivirals specified by the Project Officer.